Looking out at the Universe today, it's easy to be absolutely awed by all that we can find. The stars in our night sky are just a tiny fraction — a few thousand out of hundreds of billions — of what's present in our Milky Way. The Milky Way itself is just one lonesome galaxy out of trillions present within the observable Universe, which extends in all directions for some 46 billion light-years.

And it all began some 13.8 billion years ago from a hot, dense, rapidly expanding state known as the Big Bang. That's the first moment in which we can describe our Universe as being full of matter-and-radiation, and stepping forward from that state given the known laws of physics enables us to explain how the cosmos took its modern shape. But it's all still expanding, forming new stars, and evolving. How will it end? Here's what science has to say.